One of the more common features found in nuclear power plant designs is the use of liquid sodium to transfer heat from a reactor and to water for the generation of steam. It can also be used to transfer heat to steam to superheat the steam. In such designs, superheaters and steam generators must be designed to minimize the effects of an accidental explosion resulting from unintended contact between the steam or water and liquid sodium. In any design, a heat transfer surface between the sodium and the water or steam may fail and any contact between the water or steam and sodium can result in a pressure which will cause the failure of adjacent heat transfer surfaces and therefore, further contact between those reactants. In effect, a chain reaction occurs.
In the case of a sodium generator in which water is heated by flowing it through tubes which extend through a stream of flowing liquid sodium, a tube failure will often result in a violent reaction which will rupture adjacent tubes to cause further contact between sodium and water and an even greater pressure build-up.
Another problem which exists in sodium heated steam generators is that considerable time usually elapses before it is possible to detect the presence of the reaction. This means that considerable damage is done before it is possible to discontinue the flows of sodium and water or steam into the steam generator, and consequently, the sodium-water reaction is continuously fed with the reactants.